1. Field of the Invention
The present invention relates generally to the fabrication of semiconductor devices and to chemical mechanical polishing and planarization of semiconductor devices.
2. Background of the Related Art
In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting, and dielectric materials are deposited on or removed from a surface of a substrate. Thin layers of conducting, semiconducting, and dielectric materials may be deposited by a number of deposition techniques. Common deposition techniques in modern processing include physical vapor deposition (PVD), also known as sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and now electrochemical plating (ECP).
As layers of materials are sequentially deposited and removed, the uppermost surface of the substrate may become non-planar across its surface and require planarization. Planarizing a surface, or xe2x80x9cpolishingxe2x80x9d a surface, is a process where material is removed from the surface of the substrate to form a generally even, planar surface. Planarization is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials. Planarization is also useful in forming features on a substrate by removing excess deposited material used to fill the features and to provide an even surface for subsequent levels of metallization and processing.
Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique used to planarize substrates. CMP utilizes a chemical composition, typically a slurry or other fluid medium, for selective or non-selective removal of material from substrates. In conventional CMP techniques, a substrate carrier or polishing head is mounted on a carrier assembly and positioned in contact with a polishing pad in a CMP apparatus. The carrier assembly provides a controllable pressure to the substrate urging the substrate against the polishing pad. The pad is moved relative to the substrate by an external driving force. Thus, the CMP apparatus effects polishing or rubbing movement between the surface of the substrate and the polishing pad while dispersing a polishing composition, or slurry, to effect both chemical activity and mechanical activity.
Conventional CMP processes are performed using an abrasive article, such as a polishing composition, or slurry, containing abrasive particles in a reactive solution with a conventional polishing pad. Alternatively, the abrasive article can be a fixed abrasive article, such as a fixed abrasive polishing pad, which may be used with a CMP composition or slurry that does not contain abrasive particles. A fixed abrasive article typically comprises a backing sheet with a plurality of geometric abrasive composite elements adhered thereto.
Conventionally, in polishing substrates having features, such as a dual damascenes features formed by the deposition of a barrier layer in an aperture and a conductive material, for example copper, disposed on the barrier layer formed thereon, the conductive material is polished to the barrier layer, and then the barrier layer is polished to the underlying dielectric layer to form the feature. One challenge which is presented in polishing conductive materials is that the interface between the conductive material and the barrier layer is generally non-planar. Further, the conductive material and the barrier materials are often removed from the substrate surface at different rates, both of which can result in excess conductive material being retained on the substrate surface.
To ensure removal of all the conductive material before removing the barrier material, the conductive material may be overpolished, which often results in dishing of the conductive material in the features formed on the substrate. Dishing occurs when a portion of the surface of a metal deposited in an aperture or other substrate structure formed in a dielectric layer is excessively polished resulting in one or more concavities or depressions. Dishing performance is used to describe the ability of a CMP composition or process to polish and planarize a surface without dishing or with reduced dishing of the surface. Overpolishing or dishing of the conductive materials can result in forming topographical defects, such as concavities or depressions, and can further lead to non-uniform removal of the barrier layer disposed thereunder.
One solution to dishing is the addition of corrosion inhibitors to the CMP composition to reduce dishing, improve dishing performance, and prevent corrosion of materials during the CMP process. The corrosion inhibitors prevent or reduce the oxidation and corrosion of the metal surfaces, and allow for a more planar surface. However, CMP compositions containing corrosion inhibitors have been observed to have reduced metal dissolution during polishing and decreased solubility of polishing by-products, such as metal ions, in comparison to CMP compositions without corrosion inhibitors. The reduced metal dissolution and decreased by-product solubility in CMP compositions can result in deposition or re-deposition of metals and by-products on the substrate during the CMP process. Metals and by-products deposited during CMP processes have been observed to remain as undesirable metal residues after the CMP process which can detrimentally affect subsequent polishing processes and the polish quality of the substrate.
Therefore, there exists a need for a method and CMP composition that reduces the deposition or re-deposition of materials during CMP processing.
The invention generally provides a method and composition for planarizing a substrate surface by selective removal of a conductive material residue and a portion of the barrier layer from a substrate surface. In one aspect, the invention provides a composition adapted for selective removal of a conductive material residue and a barrier layer material in a polishing process, the composition including a chelating agent, an oxidizer, a corrosion inhibitor, abrasive particles, and water. The composition may further include one or more pH adjusting agents and/or one or more pH buffering agents.
In another aspect, the invention provides a method for selective removal of a conductive material residue and a portion of the barrier layer from a substrate surface, the method comprising applying a composition to a polishing pad, the composition comprising a chelating agent, an oxidizer, a corrosion inhibitor, abrasive particles, and water. The composition may further include one or more pH adjusting agents and/or one or more pH buffering agents.
Another aspect of the invention provides a method for processing a substrate including providing a substrate comprising a dielectric layer with feature definitions formed therein, a barrier layer conformally deposited on the dielectric layer and in the feature definitions formed therein, and a copper containing material deposited on the barrier layer and filling the feature definitions formed therein, polishing the substrate to substantially remove the conductive material, and polishing the substrate with a composition comprising a chelating agent, an oxidizer, a corrosion inhibitor, abrasive particles, and water to remove conductive material residue and a portion of the barrier layer